<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>菜鸟教程(runoob.com)</title>
</head>
<style>
.tooltip {
    position: relative;
    display: inline-block;
    border-bottom: 1px dotted black;
}

.tooltip .tooltiptext {
    visibility: hidden;
    width: 120px;
    background-color: black;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px 0;
    position: absolute;
    z-index: 1;
    top: 150%;
    left: 50%;
    margin-left: -60px;
}

.tooltip .tooltiptext::after {
    content: "";
    position: absolute;
    bottom: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: transparent transparent black transparent;
}

.tooltip:hover .tooltiptext {
    visibility: visible;
}
</style>
<body style="text-align:center">
    <h2>顶部提示框/底部箭头</h2>
    <div class="tooltip">鼠标移动到这
        <span class="tooltiptext">提示文本</span>
        </div>
</body>
</html>